In construction, air barriers control air leakage into and out of the physical separator between the interior and exterior of a building. Known air barriers may be interposed between layers of the building structural wall. Air barriers are typically also water resistive and often take the form of membranes or house wraps and provide a defined air permeance rate.
Some air barriers are also water vapour permeable, allowing the passage of water vapour while preventing the passage of air. This is made possible because the molecular structure of water vapour allows it to pass through smaller pores than oxygen and nitrogen.
Water vapour permeable air barriers in membrane form are available from numerous manufacturers including Du Pont™ (Tyvek™ Homewrap) and Fiberweb™ (Typar™ Housewrap). Self-adhering water vapour permeable air barriers in membrane form are also available from numerous manufacturers including the Henry Company and WR Grace and Co.
Existing barrier membranes typically include a water vapour permeable membrane coated on one side by an adhesive. In order to form a a substantially airtight building enclosure, sheets of the membrane are affixed to the building in an adjacent or overlapping relationship to form a building envelope. The overlapping of membranes often does not work well, as the adhesive used to affix the barrier membranes does not adhere well to other membranes. Seam tape may instead be used to ensure continuity of the air barrier/building envelope, but is cumbersome.
Thus, properly positioning and adhering adjacent sheets of material in order to form an air tight envelope around the building structure remains a challenge.
Accordingly, new water vapour permeable air tight barriers allowing formation of a better sealed building envelope are desirable.